Fast prime?

Hadley

Hadley

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James
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I've read people talking about getting a fast prime on this forum, but what exactly is a fast prime?
 
A lens with a fixed focal length and an aperture of f/2 ,1.8,1.4,1.2 (or 1.7 in some cases). Not sure if f/2.8 would fall into this class.
 
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It would be something along the lines of a 50mm f1.8 (commonly known as the nifty fifty).

Anything that only has 1 focal legth (i.e. it doesn't zoom at all) and has a wide aperture (f1.8 or wider).

The benefit of having a fast prime is that they usually produce very sharp images and they can let in a lot of light so they are useful in places with low light.
 
Hadley said:
Why do people describe them as "fast"?
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If you use a lens with a wide aperture then you can let more light in more quickly which allows you to shoot at a higher shutter speed which reduces the likelyhood of motion blur or camera shake.
 
So would it just be known as a prime if it had a high f number?
 
No it would need to be a fixed focal length, ie 35mm, 50mm, 85mm etc. Nothing that zooms.
 
And when you get one you will love it :)
 
dont want one of those then ;)
 
Hadley said:
So would it just be known as a prime if it had a high f number?
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No the opposite, the lower the 'f number' the more light that it is capable of hitting the senser. The more light, the faster the prime. Thats why you tend to find the lower the 'f number' the more expensive the lens. ;)

edited to add:

Sorry meant that whats they mean by 'fast'.
 
I didn't notice the filters, I was too blinded by "Canon" written all over everything ;)
 
Since the initial question has been answered I'll ask another question, don't worry it's Fast Prime related.

I want one for my Nikon D60, I was thinking about the 35mm f1.8 but I've noticed a lot of used Sigma 30mm f1.4 going through the classifieds at about £200. So what would you get, a used Siggy or a new Nikon?

I've discounted the idea of buying the Nikon used, they don't come up very often and are usually not cheap enough to in my eyes justify the saving over a new one.

I'm guessing in use the difference between 30mm and 35mm is hardly noticeable.

Oh and before someone says the word nifty, bare in mind I don't have an in body focusing motor.
 
i had a 35mm 1.8 DX AF-S

wish I had never sold it......:bang:...and am saving for another..!

meantime - using a 50mm f2 Ai. Manual focus and no metering
but hell they only cost £30-40 on eBay
viewfinder focus green light works
quickly correct aperture by checking image review

actually makes you "compose" the shot too
 
I'd get the new Nikon, I had it on a D90 before switching to Canon and can honestly say it was the best £180 I'd spent on a new lens....
 
Dang, what you're meant to be saying is there's not point in buying a fast prime, and that the 18-55 is the greatest technological feat known to man, and that I should be saving up my money so I can buy something sensible. At this rate I'll never own that Volvo and be destined to spend eternity driving around in my Chrysler Neon.
 
Take a nice picture of the Neon with your new prime :)
 
KC Leblanc said:
Oh and before someone says the word nifty, bare in mind I don't have an in body focusing motor.
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can someone explain this bit for me please ,,,its gone over my head ,, ( i'm a shortarse )
 
donutagain said:
can someone explain this bit for me please ,,,its gone over my head ,, ( i'm a shortarse )
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Both Nikon and Canon do a very cheap 50mm primes (which have become known as nifty fifties). However my cheap Nikon body doesn't have a focusing motor built into the body, it instead relies in the lens having it's own motor. Tthe cheap Nikon 50mm doesn't have it's own motor, so on my camera would become manual focus.
 
yes but the nifty part of ..nifty fifty ...has nothing to do with its focusing ability ,,,you can still have a manual focus nifty fifty .
 
Yep - about £25 if you look around :)
 
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